Heating Elements for Experiments

[delta720]

Hi,

As part of my final year project I have to heat air within an exclosed environment (i.e. a 1m x 1m x 1m insulated box) to test the effectiveness of using phase change materials to regulate ambient air temperature.

To do this I need to slowly heat the air inside the box at a rate that will allow the walls (plasterboard) to increase in temperature roughly at the same rate as the air.


A similar experimant was done in my college several years ago and that student used a 200W light bulb, however it took around 12 hours to increase the temperature by 8 degrees, so there was clearly massive heat loss.

I've thought of using a low power fan heater but I think the fan blowing the hot air will result in the thermometers picking up a higher temperature then what the walls actually are. If i just use the heating element from the fan and allow convection currents to form in the box to slowly heat all the walls would this result in the element overheating and pose a fire risk?

Cheers,

Dave

 

[vk6kro]

The fan heater seems like a good idea, however there has to be an actual air flow. You can't blow air into a sealed box, so you need an exit for the air. This should be well away from the input, though.

The element of a fan heater is designed to have air flowing across it or it will overheat, as you mention. Try blocking the air flow and watch the element go red hot.

You can measure the air temperature at a place in the box which is not directly in the path of the air flow. This would be better if you cut the air flow from the fan heater for a minute or so before you take the measurement.

You can get probe thermometers which have a digital thermometer attached to a rigid rod which you can poke through a hole to measure temperature.
You could have several holes and keep records for each hole.

You can buy replacement elements for ovens but these require mains voltage, so you would need to get it wired up safely.

Blankets or pieces of carpeting will help insulate the box if you attach them to the outside of the box.

 

[BilPrestonEsq]

How about FOUR 200w light bulbs!

 

[vk6kro]

How about FOUR 200w light bulbs!

Maybe, but you would need some fans in there as well.

Just a suggestion, but, how would it go if you put the fan heater inside the box.

Then it would get air that was already heated and heat it some more as well as spreading it around the inside of the box.

You would have to monitor the temperature or it could become a fan forced oven and melt the plastic of the heater.